Electric furnace



Feb..13, 1923. 1,444,948.

0. H. CARPENTER.

ELECTRIC FURNACE."

HLED APR. 23. I920.

INVENTQR Cra/uibn/iC'a/peflikr 7 g 4 2 f/ ATTORNEY WITNESSES:

entree s'rA'rEs Sit J ANIE...

KRTEENTER, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOB TO WEST- ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENN- ELECTRIC FURNACE.

Application filed April 23, 1920. Serial No. 375,994.

concern:

1, Cameron H. CARPEN- United tates, and a smirg, in the county of of Pennsylvania, have I a new useful lmpro'vemcnt in ric surnznres, of which the following is 1 relates to electric furnaces, l to rnaces of the electrich the container for the as the resistor to furnish .cssary to melt or to heat-treat rent to and from the crucible resistor which means all permit ofheinp readily renewed or replaced. i am aware that a container ising a m'aphite crucible has been used as a. resist ipparently little commercial success :nded the use of such graphite containers as resistors which I believe to be due to the method of conducting the current into and out of t crucible.

ln practicing my invention, 1 provide a graphite container, into which material to be melted or to he heat-treated, may be placed. and mouit the same in a suitable r l provic.v mprovcd means for makcctrical contact with the crucible, these means comprisii'ur masses of electrical-com packed or tanuied into close contact with part of the outer surface of the container to conduct the. current to and from the crucihle.

1n the single sheet of drawings, Figure 1 is a cross-sectional View along the line 1-1 of F 2 of a. furnace embodying my invention; F'gr. 2 is a view of the same furnace along the line ll--ll of Fig. 1. Fig. 3 is a View, in section, on the line III-IlI of Fig. 4, of a modification of a furna ,emh i dying my invention, and. Fig. 4 is a view on the line lV-lV of Fig. 3.

The supporting: structure of the furnace coi-Tiprises an exterior metal casing or frame 1 which encloses an outer shell 2 of heatinsulatinp: l'a'iclr and an inner shell 3 of fire brick. In tr furnace shown in Figs. 1 and 2, the inner alls of the shell 3 are spaced apart to form a substantially circular chamher 4 and two lateral extensions 5 for a purpose to be hereinafter set forth. A graphite crucible 6 is placed in the inner chamber 4., the chamber being of such outline as to conform closely to the shape of the crucible 6. In each of the extensions 5 is placed a mass 7 of electrical-conducting granular material, such as graphite or coke, and a ter minal electrode 8, con'iprising a block of carbon or amorphous graphite, is so located that its inner end extends a relatively short distance into the well 5 The terminal electrodes 8 extend outwardlfx through the casin; 1. and a metal terminal plate is suitably secured thereto for connection to the electric supply-circuit conductors (not shown). The

granular material 7 is thoroughly tamped in place in the wells 5 so that it may closely engage not only the terminal electrode 8 but also a portion of the outer surface of the graphite crucible 6 and thus constitute a conducting path of relatively low resistance therehetween.

Both the current-carrying part of the outer surface of the crucible 6 and the granular material 7 will oxidize during the operation of the furnace and, as the wells 5 are open at the top of the furnace, it is an easy matter to thoroughly pack or tainp the granular material solidly in the wells 5 as soon as sufficient oxidation and burning away of the granular material has taken place to make such renamping necessary. It is also easy to remove the oxidized material and'renew it in case such procedure should become necessary.

Referring particularly to Figs. 3 and 4, wherein I have illustrated a modification of the device shown in Figs. 1 and 2, it may be noted that the method of conducting current to and from the graphite muflle 9 is substantially the same as described above. Similar wells 5 are providedin the inner shell 3, and a mass of granular electricalconducting material 7 is placed therein, a solid terminal electrode 8 projecting into the wells 5, as described above. The operation of the modification of my furnace, as shown in Figs 3 and 4, is substantially the same as that shown in Figs. 1 and 2 and this modification may be used to heattreat metal objects. If the mufile 9, which comprises a member of substantially tubular shape, is placed in a horizontal position, as 4 the mufiie 9 is placed in a suhstantiallyvertical position. the articles may be drawn therethrough in a substantially vertical path and he heat-treated while in the mut'tle. I thus provide new and improved means for making electrical contact with an electrical conducting mulile' which acts not only as a container for the material being treated but also as a resistor to generate the necessary heat, I provide also relatively simple means for insu ing; that the contact resistance between the mutlle and the co-operating contact member shall he maintained at a relatively lou value during long periods of operation of the furnace.

While I have shown a specific eu'ihodinarnt of my invention, various changes may he made therein without departing: from the spirit and scope of my invention and 1 desire that only such lin'iitations shall he placed thereon as are imposed by the prior art or are specifically set forth in the appended claims.

I claim as my invem ionz 1. In an electric furnace. the coml'iination with a refractory casing. of muille'ot' refractory electrical-cowlacting material in said casing. hoppers in said using on opposite sides of said mutlie, solid carbonaceous honaceous terminal, electrodesextending into said-hop- 'pers, and a mass of clectrical-condacting granular material in each. oi said hoppers adapted to electrically connect said el,ec-

t-onducting granular material interposed between said electrodes and said nurllle. said masses of granular material being of greater cross-section than the electrodes to prevent oven-heating of the same.

Tn testimony \vhereofil have hereunto subscribed my name this th day of March,

cna'asrou n. ("ARPENTER 

